Latex binder compositions

ABSTRACT

A latex binder composition which is the reaction product of a conjugated diene monomer and a vinyl-substituted aromatic monomer along with minor amounts of other comonomers including acrylamide or a derivative thereof, methacrylic acid, N-methylolacrylamide, and optional unsaturated carboxylic acids, has an average particle size of less than 1,500 Å. The latex binder which has good stability can be used on nonwoven cellulosic based substrates to impart high wet tensile strength thereto.

FIELD OF INVENTION

The invention relates to aqueous latices and, more particularly, tosynthetic latices of multicomponent copolymers which exhibit excellentlong-term colloidal stability and which impart exceptional wet tensilestrength to nonwoven cellulosic based substrates to which they areapplied.

BACKGROUND

Various synthetic latices have heretofore been commonly used for bondingtogether filaments or fibers of nonwoven fabrics to form durableindustrial wipes or toweling. Such compositions must meet a number oftechnical and practical requirements. In particular, the latexcomposition, after having been applied to a nonwoven cellulosic basedsubstrate and subsequently dried, should produce a fabric which is soft,flexible, and nonabrasive, and which has good tensile strength whenwetted by water or various solvents.

It is preferred that the latex compositions used as binders for nonwovencellulosic based substrates should not cause undesirable discolorationor yellowing of the fabric. It is also preferred that such compositionsexhibit good long-term colloidal stability and good mechanical stabilityunder high shear to avoid excessive build-up of latex particles on spraynozzles used for applying the latex to the substrate.

Known synthetic latices suitable for binding the fibers of nonwovensubstrates include aqueous emulsions of multicomponent copolymerscomprised primarily of styrene and butadiene. With such conventionalprior art compositions, it has generally been necessary to utilize highamounts of melamine formaldehyde resins and/or high amounts ofN-methylolacrylamide monomers.

A disadvantage with such compositions is that they contain or generaterelatively high amounts of free formaldehyde which is now regarded asbeing highly undesirable from an environmental standpoint.

Accordingly, it would be highly desirable to provide an inexpensivelatex binder capable of achieving high wet tear strength while reducingthe need for melamine formaldehyde resins and/or N-methylolacrylamidemonomers.

SUMMARY OF INVENTION

The compositions of the invention generally comprise a binder dispersedin water wherein the binder is the polymerization product of primary orprincipal monomers generally utilized in large amounts and other minoror secondary monomers utilized in lesser amounts. For purposes ofclarity, the amounts of the various minor monomers are based upon 100parts by weight of all of the primary monomers utilized. Of course, anyproportion or fraction thereof can be utilized. The polymerizationproduct is made from one or more conjugated diene primary monomers andone or more vinyl-substituted aromatic primary monomers. As noted, basedupon 100 parts by weight of the primary monomers, that is the one ormore conjugated dienes and the one or more vinyl substituted aromaticmonomers, various other monomers are utilized such as from about 0.1 toabout 3 parts by weight of an acrylamide monomer or derivative thereof,from about 0.1 to about 6 parts by weight of methacrylic acid, fromabout 0.1 to about 5 parts by weight of a N-methylolacrylamide monomeror derivative thereof, and optionally from about 0.1 to about 10 partsby weight of an unsaturated carboxylic acid monomer other thanmethacrylic acid.

It has been discovered that nonwoven cellulosic based substrates treatedwith the latex compositions of the invention generally have better wettensile strength when the average particle size of the polymeric binderis small. More particularly, it has been discovered that a dramaticimprovement in wet tensile strength is achieved when the averageparticle size is reduced from typical prior art dimensions of about1,800 Å to below 1,500 Å.

Another aspect of the present invention involves the use of anionicalkylated disulfonated diphenyl oxide surfactants and/or alkylsulfosuccinate surfactants to provide an emulsion polymerization ofmonomers capable of achieving a desired average particle size of thepolymeric binder, good long-term colloidal stability, and a latex havinglow residual monomer levels.

DETAILED DESCRIPTION

The latex binder compositions of the invention are generally formed byemulsion polymerization techniques which are well known to the art andto the literature. The polymeric binder is comprised primarily of thereaction product of one or more conjugated diene monomers and one ormore vinyl-substituted aromatic monomers.

Suitable conjugated diene monomers generally contain from about 4 to 8carbon atoms and desirably from about 4 to 6 carbon atoms. Examples ofspecific diene monomers include piperylene, isoprene,2,3-dimethyl-1,3-butadiene, and preferably butadiene. Mixtures of two ormore conjugated dienes can also be utilized.

Suitable vinyl-substituted aromatic monomers generally contain from 8 toabout 12 carbon atoms. Specific examples include alpha-methyl styrene,p-tertiary butyl styrene, methyl vinyl toluene, p-vinyl toluene, 3-ethylstyrene, and the like, with styrene being preferred. Mixtures of two ormore vinyl-substituted aromatic monomers can also be utilized.

Based upon 100 parts by weight of the primary monomers, i.e., the one ormore conjugated diene monomers and one or more vinyl-substitutedaromatic monomers, the amount of conjugated dierio monomers is generallyfrom about 30 to about 70 parts by weight, and preferably from about 50to about 65 parts by weight. The amount of the one or more vinylsubstituted aromatic monomers which is utilized is thus the differencebased upon 100 parts by weight of the primary monomers and is hencegenerally from about 70 to about 30, and preferably from about 50 toabout 35 parts by weight.

The polymeric binder also contains from about 0.1 to about 3 parts anddesirably from about 0.5 parts to about 2.0 parts by weight per 100parts by weight of the primary monomers (PHPM), that is, the one or moreconjugated dierio monomers and the one or more vinyl-substitutedaromatic monomers, of an acrylamide monomer or a derivative thereof,such as N-alkyl acrylamide, N,N-dialkyl acrylamide or dialkylacrylamide, or a N,N-cycloalkyl acrylamide. The alkyl group generallyhas from 1 to 8 carbon atoms with specific examples including methyl,ethyl, and isopropyl. Examples of specific compounds includeN,N-dimethyl-acrylamide and N,N-cyclohexyl acrylamide, with acrylamidebeing preferred.

The polymeric binder of the invention also include from about 0.1 toabout 6 parts by weight and desirably from about 0.5 to about 2.0 partsby weight PHPM of mothacrylic acid to enhance colloidal stability. It isan important aspect of the present invention that the latex bindercomposition be free of or at the most contain small amounts of acrylicacid, that is generally less than 2 and desirably less than 0.5 parts byweight PHPM inasmuch as substantial amounts of this acid generally leadsto colloidal instability.

The amount of N-methylolacrylamide monomer or derivative thereof is lowand is from about 0.1 to about 5 parts by weight, desirably from about0.5 to about 3 parts by weight, and preferably from about 1.0 to about2.5 parts by weight PHPM. Such compounds generally includeN-methylol-functional ethylenically unsaturated monomers includingN-methylolamides of ethylenically unsaturated carboxylic acids having3-10 carbons, such as N-methylolacrylamide, N-methylolmethacrylamide,N-methylolmaleimide, N-methylol-maleinamic acid, N-methylol-maleinamicacid esters, N-methylolamides of the vinyl aromatic acids such asN-methylol-p-vinylbenzamide, and the like.

Optional preferred monomers which can be used in forming the polymericbinders of the invention include one or more unsaturated carboxyticacids containing from about 3 to about 12 carbon atoms other than theabove noted methacrylic acid and the absence or general exclusion ofacrylic acid. Such monomers improve the colloidal stability of latexcompositions and the amount thereof generally ranges from about 0.1 toabout 10 parts by weight, desirably from about 0.5 to about 5 parts byweight, and preferably from about 1 to about 3 parts by weight PHPM.Examples of suitable unsaturated carboxylic acid monomers include maleicacid, citraconic acid, fumaric acid, itaconic acid, and the like, aswell as combinations thereof. Fumaric and itaconic acid are preferred.

Other optional monomers which can be utilized to prepare the latexbinder copolymers of the present invention include vinyl chloride,vinylidene chloride, and the like in amounts from about 0.1 to about 30parts by weight and preferably from about 2 to about 15 parts by weightPHPM.

Still another optional monomer is acrylonitrile or various alkylderivatives thereof wherein the alkyl group contains from 1 to 6 carbonatoms with specific examples including methacrylonitrile,crotononitrile, and 2-pentenenitrile. The amount of such optionalmonomers is generally from about 0.1 to about 30 and desirably fromabout 2 to about 15 parts by weight PHPM.

Still another optional monomer are the various alkyl(meth) acrylateesters and hydroxyl derivatives thereof, wherein the alkyl portion hasfrom 1 to about 10 carbon atoms with specific examples including butylacrylate, 2-ethylhexyl acrylate, propyl acrylate, ethyl acrylate,hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxymethylacrylate, hydroxymethyl methacrylate, and the like. The amounts of suchester monomers, when used can generally range from about 0.1 to about30, and preferably from about 2 to about 15 parts by weight PHPM.

Chelating agents can be utilized during polymerization to tie-up variousmetal impurities as well as to achieve a uniform polymerization. Theamounts of such chelating agents are generally small, such as from about0.01 to about 0.25 parts by weight PHPM. Examples of suitable chelatingagents include ethylene diamine tetraacetic acid, nitrilotriacetic acid,citric acid, and their ammonium, potassium, and sodium salts.

The above monomers are polymerized in the presence of water to form thelatex binder of the present invention in accordance with conventionalemulsion polymerization procedures and techniques. Free radicalinitiators are typically utilized as well as optional chain transferagents.

The free radical initiators utilized to polymerize the variousabove-described latex binder-forming monomers include sodium persulfate,ammonium persulfate, potassium persulfate, and the like. Other freeradical initiators can be utilized which decompose or become active atthe temperature utilized during polymerization such as variousperoxides, e.g., cumene hydroperoxide, dibenzoyl peroxide, diacetylperoxide, dodecanoyl peroxide, di-t-butyl peroxide, dilauroyl peroxide,bis(p-methoxy benzoyl) peroxide, t-butyl peroxy pivalate, dicumylperoxide, isopropyl percarbonate, di-sec-butyt peroxy dicarbonate,various azo initiators such as azobisdimethylvaleronitrile,2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis-2-methylbutyronitrile,2,2'-azobis(methylisobutyrate), and the like, and mixtures thereof. Theamount of the free radical initiator is generally from about 0.25 toabout 2.0, and preferably from about 0.5 to about 1.5 parts by weightPHPM.

Optional chain transfer agents include mercaptans such as the alkyland/or aralkyl mercaptans having from 8 to about 18 carbon atoms andpreferably from about 12 to about 14 carbon atoms. The tertiary alkylmercaptans having from 12 to 14 carbon atoms are highly preferred.Examples of suitable mercaptans include N-octyl mercaptan, N-dodecylmercaptan, t-octyl mercaptan, t-dodecyl mercaptan, tridecyl mercaptan,tetradecyl mercaptan, hexadecyl mercaptan, and the like, as well asmixtures thereof. The amount of the chain transfer agent utilized isgenerally, from about 0.01 to about 5 parts by weight PHPM.

In accordance with an important aspect of the invention, the emulsifiersor surfactants utilized are preferably an alkylated disulfonateddiphenyl oxide surfactant and/or an alkyl sulfosuccinate surfactant.Suitable alkylated disulfonated diphenyl oxide surfactants are generallyrepresented by the formula: ##STR1## wherein R¹ and R², independentlyare hydrogen or a linear, branched, or cycloalkyl containing from about6 to about 16 carbon atoms, preferably from about 10 to about 14 carbonatoms, provided that R¹ and R² are not both hydrogen, and X,independently is a suitable cation. Suitable cations include sodium andother alkali metal ions, alkyl quaternary amine ions wherein the alkylgroup has from 1 to 6 carbon atoms such as triethyl quaternary amine andisopropyl quaternary amine, as well as other organic cations.

Preferred diphenyl oxide surfactants include compounds wherein X issodium and R¹ and R², independently, are hydrogen and dodecyl, ordodecyl and dodecyl, respectively. Such surfactants are commerciallyavailable from Dow Chemical as Dowfax 2A1.

Suitable alkyl sulfosuccinate surfactants include those represented bythe formula: ##STR2## wherein R³ and R⁴ are, independently, a branched,linear, or cycloalkyl group containing from 4 to about 18 carbon atoms,desirably from 4 to 8 carbon atoms, and X is a suitable cation. Suitablecations for the alkylated sulfosuccinate surfactant are generally thesame as those for the alkylated disulfonated diphenyl oxide surfactantwith the sodium cation being preferred. Preferred R³ and R⁴ groupsinclude butyl, hexyl, or a cyclohexyl group with a preferred X groupbeing sodium. A particularly preferred alkylated surfactant is sodiumdicyclohexyl sulfosuccinate which is available from Cytex Industries asAerosol A196, and sodium dihexyl sulfosuccinate available as Aerosol MA.

The alkylated disulfonated diphenyl oxide surfactants, when used alone,are generally present in amounts ranging from about 0.1 to about 3parts, and desirably from about 0.50 to about 1.5 parts by weight PHPM.

The alkyl sulfosuccinate surfactants are generally utilized in amountsranging from about 0.1 to about 3.0 parts by weight and desirably fromabout 0.5 to about 1.5 part by weight PHPM. Desirably, the variousalkylated disulfonated diphenyl oxide surfactants are used incombination with the alkyl sulfosuccinate surfactants.

Various anionic surfactants can be utilized, such as various alkylsulfates, various alkyl aryl sulfonates, various α-olefin sulfonates,various amine salts, and the like, wherein the alkyl portion generallyhas from about 6 to about 20 carbon atoms such as sodium lauryl sulfate,sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate. However,inasmuch as such surfactants generally yield unsuitable properties suchas colloidal stability, wet tensile strength and the like, whenutilized, the amount thereof is generally one part or less by weight,desirably 0.5 parts or less by weight, and preferably 0.25 parts byweight or less PHPM.

Another advantage is that the latex binder compositions of the presentinvention generally have a reduced formaldehyde content of generallyless than 150 parts per million, desirably less than 100 parts permillion and preferably less than 75 parts per million of formaldehydefor every 100 parts by weight of latex binder.

Still another advantage of the latex binder composition per se is thatmanufacture of the polymer binder is relative easy due to improvedcolloidal stability, lack of build-up of solid polymer in walls of thereactor, and lower amounts of coagulant dispersed in the latex.

The various latex-forming monomers of the present invention arepolymerized by free radicals by any conventional method including batch,incremental, or continuous, in the presence of an effective amount ofwater to enable the formation of an emulsion as well as proper mixing ofthe various additives, heat transfer, and the like. Polymerization isgenerally carried out from about 55° C. to about 95° C., and desirablyfrom about 60° C. to about 75° C. Polymerization is generally conductedin an acidic medium when acidic monomers are utilized and the pH of thelatex binder is generally from about 1.5 to about 6.5 with from about2.0 to about 4.0 being preferred. The amount of solids, that is, thecopolymer or binder, is generally from about 35 to about 60, andpreferably from about 40 to about 50 percent by weight based upon thetotal weight of the binder and the remaining ingredients, for example,water.

In accordance with the principles of the invention, the average particlesize of the binders after filtering is generally from about 1,000 toabout 1,500 Å, and more preferably from about 1,200 to about 1,400 Å. Itis believed that the lower particle sizes, as compared with the priorart which generally ranges from about 1,800 to 2,100 Å, are particularlyresponsible for the improved wet tear strength of non-woven cellulosicbased or polyester based substrates which have been treated with thelatex binder of the invention.

The latex binder compositions of the invention have been found toexhibit good long-term colloidal stability, that is, the polymericbinder particles do not tend to coagulate or agglomerate to render thecomposition useless for its intended purpose. Thus, very low levels ofcoagulant, especially fine-size coagulants such as would be retained ona 325 Tyler mesh, exist after filtering of the latex. Such levels aregenerally 0.1 percent or less, desirably 0.05 percent or less, and moredesirably 0.02 percent or less, and preferably 0.01 percent or less byweight based upon the total weight of the latex solids. Anotheradvantage of the present invention is high conversion of all themonomers such as at least 95 percent thereof, desirably at least 97 or98 percent and preferably at least 99 percent of all monomers.

The latex binder of the present invention has many applications and canbe utilized on non-woven celtulosic based substrates such as paper,cotton, and the like wherein the majority amount of the substrate is anatural organic material. The substrate can also include minor amountsof other fibers such as polyester, nylons, acrylates, and the like.Examples of such substrates include paper towels, various paper tapes,paper containers, industrial towels, industrial wipes, and the like.

The latex binder can also be applied to various nonwoven fibers such aspolyester, polypropylene, rayon, nylon, and other synthetic fibers, andcombinations thereof.

With regard to the present invention, "high wet tensile strength" meansthat the fabric has a high tensile strength when saturated with water oran organic solvent such as toluene, mineral spirits, or heptane.

The invention will be better understood by reference to the followingexamples which serve to illustrate but not limit the invention.

EXAMPLES

Apparatus

A one-gallon, stainless steel pressure reactor equipped with monomeraddition ports, stirrer and temperature and pressure measurement deviceswas used. Cooling was provided by an external water bath.

Example 1

A mixture of deionized water 1000 g, Dowfax 2A1 (15 percent) 50g,itaconic acid 22g, Aerosol A196 (10 percent) 150g, EDTA solution (40percent) 4 g and styrene 112 g were stirred and heated to 65° C. (undernitrogen). A solution of sodium persulfate 7.5 g in deionized water 142g was then added to the reactor. After 30 minutes, the monomer andaqueous streams, as set forth in Table I were added to the reactor at60° C. over a period of 51/2 hours.

After 5.5 hours, the temperature was raised to 71° C. and the reactioncontinued for 4 hours (total solids approximately 45 percent). The pH ofthe latex binder was 2.5. The conversion of monomers to polymer was 99percent.

                  TABLE I                                                         ______________________________________                                        AQUEOUS STREAM  MONOMER STREAM                                                ______________________________________                                        D. I. Water 330 g                                                                             Styrene 522 g                                                 Dowfax 2A1 (15%) 80 g                                                                         Butadiene 732 g                                                               Acrylamide (50%) 75.3 g                                                       Divinyl Benzene (55%) 7.5 g                                                   Methacrylic Acid 30 g                                                         N-Methylolacrylamide (48%) 78 g                                               Dodecyl Mercaptan 7.5 g                                       ______________________________________                                    

Post Addition restorage and Stability

The following was added to the reactor and then the latex wassteam-stripped and filtered in a conventional manner.

Dowfax 2A1 (15 percent) 20 g, D.I. water 82 g, 28% ammonia 25 g, DREW L198 antifoam 4 g, Proxel GXL (25%) biocide 8 g, Bostex 490B (35%)antioxidant 45 g.

    ______________________________________                                        Properties:                                                                   ______________________________________                                        Total solids content: 44.6 percent                                            pH:                   6.8                                                     Surface tension:      47 dynes/cm                                             Brookfield viscosity: 500 cps                                                 Particle size:        1280 Å                                              Coagulation collected 0.1 grams                                               on 325 Tyler mesh:                                                            ______________________________________                                    

Example 2

A binder composition having only 16.9 g of Aerosol MA (80%) instead ofAerosol A196 and Dowfax 2A1 as in Example 1, was prepared by a similarprocess and method. The properties of this binder are shown in Table II.It can be seen that the particle size is rather large and that thetensile strengths are inferior to those of Example 1.

Examples 3 and 4

In a similar fashion to Example 1, the Aerosol A196 and Dowfax 2A1 werereplaced on an equal weight basis with sodium dodecyl sulfate (Example3) and sodium dodecyl benzene sulfonate (Example 4). These surfactantsare outside the scope of the surfactants of the present invention.

Although the tensile strengths of latex compositions 3 and 4 aresomewhat similar to Example 1, the conversion of monomers to polymer wastoo low to be practical and the levels of coagulum retained on 325 meshwas unduly high at 6g for Example 3 and 7 g for Example 4.

Each of the latexes in Table II were applied to Whatman sheets and driedat room temperature and then cured for 5 minutes at 315° F. (158° C.).The amount of latex applied in each case was 20 percent by weight (45percent solids) of the total weight of the latex and paper.

The dried sheets where then tested for wet tensile strength (in water),and solvent tensile strength using a variety of different solvents suchas toluene, heptane, mineral spirits. The solvent tensile test is anaverage tensile strength of paper soaked in toluene, heptane and mineralspirits for a period of 3 hours and tested immediately thereafterwithout drying. The results indicate that the latex compositions of theinvention have much better wet tear strength and average solvent tearstrength than the control (Example 2).

The results demonstrate the effectiveness of the composition ofExample 1. The higher wet tensile strength of this latex when formulatedin a non-woven system allows for the reduction or elimination ofmelamine formaldehyde resins with a reduction in formaldehyde dehydecontent of approximately 66 percent (300 ppm versus 100 ppm HCHO).

                                      TABLE II                                    __________________________________________________________________________                                      AVERAGE                                                     MONOMER           SOLVENT                                            SURFACTANT                                                                             CONVERSION                                                                             WET TENSILE                                                                            TENSILE                                                                              PARTICLE                             EXAMPLE                                                                              SYSTEM   (%)      (LBS.)   (LBS.) SIZE (Å)                         __________________________________________________________________________    1      Dowfax 2A1/                                                                            99       33       40     1280                                        Aerosol A196                                                           2 (Control)                                                                          Aerosol MA 80                                                                          97       23       33     2000                                 3      Avirol 2020                                                                            88       30       36      770                                        (SDS)                                                                  4      Siponate LDS                                                                           79.6     29       37      772                                        (SDBS)                                                                 __________________________________________________________________________     Aerosol MA 80 = Sodium Dihexyl Sulfosuccinate.                                SDS = Sodium Dodecyl Sulfate.                                                 SDBS = Sodium Dodecyl Benzene Sulfonate.                                 

While in accordance with the patent statutes the best mode and preferredembodiment has been set forth, the scope of the invention is not limitedthereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A latex binder composition comprising;a binderdispersed in water, said binder being the reaction product of monomersconsisting essentially of(a) from about 30 to about 70 parts by weightof one or more conjugated diene monomers having from 4 to 8 carbon atomsand (b) from about 70 to about 30 parts by weight of one or morevinyl-substituted aromatic monomers having from 8 to 12 carbon atoms,the total amount of said (a) and (b) monomers being 100 parts by weight,and from about 0.1 to about 3 parts by weight of an acrylamide monomeror a derivative thereof wherein said derivative is N-alkyl acrylamide,N,N-dialkyl acrylamide, dialkyl acrylamide or N,N-cycloalkyl acrylamide,or combinations thereof, and wherein said alkyl group has from 1 to 8carbon atoms, and optionally from about 0.1 to about 10 parts by weightof an unsaturated carboxylic acid monomer other than methacrylic acidand less than 2 parts by weight of acrylic acid, for every 100 parts byweight of said one or more (a) and (b) monomers, and from about 0.1 toabout 6 parts by weight of a methacrylic acid monomer and from about 0.1to about 5 parts by weight of N-methylol-functional ethylenicallyunsaturated monomer which is N-methylolacrylamide orN-methylolmethacramide or both including derivatives thereof, for every100 parts by weight of said (a) and (b) monomers, and said latex binderhaving an average particle size of less than 1,500 Å.
 2. A latex binderaccording to claim 1, wherein said particle size is from about 1,000 Åto about 1,500 Å.
 3. A latex binder according to claim 2, wherein theamount of said optical acrylic acid is less than 0.5 parts by weight,wherein said binder has a formaldehyde content of less than 150 parts byweight per million parts by weight of said latex binder, wherein saidlatex has less than 0.1 percent by weight of coagulant retained on 325Tyler mesh based upon the total weight of the solids of said latexbinder composition, and wherein the conversion of all of said monomersis at least 95 percent.
 4. A latex binder composition according to claim3, wherein said (a) conjugated diene monomer is butadiene, wherein said(b) vinyl substituted aromatic monomer is styrene, wherein the amount ofsaid butadiene monomer is from about 50 to about 65 parts by weight,wherein the amount of said styrene monomer is from about 50 to about 35parts by weight, wherein said acrylamide monomer or derivative thereofis acrylamide in an amount of from about 0.5 to about 2.0 parts byweight, wherein the amount of said methacrylic acid is from about 0.5 toabout 2.0 parts by weight, wherein said N-methylol-functional typecompound is N-methylolacrylamide in an amount of from about 0.5 to about3 parts by weight, wherein said particle size is from about 1,200 toabout 1,400 Å, and wherein said formaldehyde content is less than 100parts per million.
 5. A latex binder composition comprising; a binderdispersed in water, said binder being the reaction product of monomersconsisting essentially of(a) from about 30 to about 70 parts by weightof one or more conjugated diene monomers having from 4 to 8 carbon atomsand (b) from about 70 to about 30 parts by weight of one or morevinyl-substituted aromatic monomers having from 8 to 12 carbon atoms,the total amount of said (a) and (b) monomers being 100 parts by weight,andfrom about 0.1 to about 3 parts by weight of an acrylamide monomer ora derivative thereof wherein said derivative is N-alkyl acrylamide,N,N-dialkyl acrylamide, dialkyl acrylamide, or N,N-cycloalkylacrylamide, or combinations thereof, and wherein said alkyl group hasfrom 1 to 8 carbon atoms, from about 0.1 to about 6 parts by weight ofmethacrylic acid, and from about 0.1 to about 5 parts by weight ofN-methylol-functional ethylenically unsaturated monomer which isN-methylolacrylamide or N-methylolmethacrylamide or both includingderivatives thereof, and optionally from about 0.1 to about 10 parts byweight of an unsaturated carboxylic acid monomer other than methacrylicacid and less than 2 parts by weight of acrylic acid, for every 100parts by weight of said one or more (a) and (b) monomers, said latexbinder having an average particle size of less than 1,500 Å, theconversion of said monomers being at least 95 percent, and said binderhaving a formaldehyde content of less than 150 parts by weight permillion parts by weight of said binder, and from about 0.1 to about 3parts by weight of an alkylated disulfonated diphenyl oxide surfactantor from about 0.2 to about 2.0 parts by weight of an alkylsulfosuccinate surfactant, or combinations thereof, for every 100 partsby weight of said primary monomers.
 6. A latex binder compositionaccording to claim 5, wherein said particles size is from about 1,200 toabout 1,400 Å, wherein said alkylated disolfonated diphenyoxidesurfactant is sodium dodecyldiphenyloxide disulfonic acid, wherein saidalkyl sulfosuccinate surfactant is sodium dicyclophexyl sulfosuccinate,wherein said conversion of said monomers is at least 98 percent, andwherein said formaldehyde level is 100 parts by weight or less permillion parts by weight of said binder.
 7. A latex bindex composition,comprising;a binder dispersed in water, said binder being thepolymerization product of monomers comprising;(a) from about 30 to about70 parts by weight of one or more conjugated diene monomers having from4 to 8 carbon atoms and (b) from about 70 to about 30 parts by weight ofone or more vinyl-substituted aromatic monomers having from 8 to 12carbon atoms, the total amount of said (a) and (b) monomers being 100parts by weight, and from about 0.1 to about 6 parts by weight ofmothacrylic acid, and optionally from about 0.1 to about 10 parts byweight of an unsaturated carboxylic acid monomer other than mothacrylicacid and less than 2 parts by weight of acrylic acid, for every 100parts by weight of said one or more (a) and (b) monomers, andamide-containing monomers consisting of 1) an acrylamide monomer or aderivative thereof wherein said derivative is an N-alkyl acrylamide,N,N-dialkyl acrylamide, dialkyl acrylamide, or N,N-cycloalkylacrylamide, or combinations thereof, wherein said alkyl portion has from1 to 8 carbon atoms, and 2) an N-methylolacrylamide monomer or anN-methylolmethacrylamide monomer or both or a derivative thereof,wherein the amount of said acrylamide monomer or derivative thereof isfrom about 0.1 to about 3 parts by weight and wherein the amount of saidN-methylolacrylamide or said N-methylolmethacrylamide monomer or both ora derivative thereof is from about 0.1 to about 5 parts by weight, forevery 100 parts by weight of said one or more (a) and (b) monomers, saidbinder having an average particle size of less than 1,500 Å, and havinga formaldehyde content of less than 150 parts by weight per millionparts by weight of said binder.